Interaction of Charged Colloidal Particles at the Air–Water Interface

Girotto, Matheus; Santos, Alexandre Pereira dos; Levin, Yan

doi:10.1021/acs.jpcb.5b10105

Cited by 29 publications

(29 citation statements)

References 49 publications

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“…(14) and (15). The black dashed curves correspond to the "simplified" QCA given by analytical expressions (19) and (20). The agreement between the two versions of QCA and MD dispersions is satisfactory at sufficiently long wavelengths (q 2 for the longitudinal and q 3 for the transverse mode).…”

Section: B Collective Modesmentioning

confidence: 93%

Thermodynamics and dynamics of two-dimensional systems with dipolelike repulsive interactions

2018

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Thermodynamics and dynamics of a classical two-dimensional system with dipolelike isotropic repulsive interactions are studied systematically using extensive molecular dynamics (MD) simulations supplemented by appropriate theoretical approximations. This interaction potential, which decays as an inverse cube of the interparticle distance, belongs to the class of very soft long-ranged interactions. As a result, the investigated system exhibits certain universal properties that are also shared by other related soft-interacting particle systems (like, for instance, the one-component plasma and weakly screened Coulomb systems). These universalities are explored in this article to construct a simple and reliable description of the system thermodynamics. In particular, Helmholtz free energies of the fluid and solid phases are derived, from which the location of the fluid-solid coexistence is determined. The quasicrystalline approximation is applied to the description of collective modes in dipole fluids. Its simplification, previously validated on strongly coupled plasma fluids, is used to derive explicit analytic dispersion relations for the longitudinal and transverse wave modes, which compare satisfactory with those obtained from direct MD simulations in the long-wavelength regime. Sound velocities of the dipole fluids and solids are derived and analyzed.

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Section: B Collective Modesmentioning

confidence: 93%

Thermodynamics and dynamics of two-dimensional systems with dipolelike repulsive interactions

2018

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“…The difficulty, however, arises when the simulation cell is bounded by the polarizable surfaces such as metal electrodes or phospholipid membranes. If there is only one polarizable surface present, it is straightforward to extend the techniques described above using the usual image charge construction [35][36][37][38][39][40][41] . However, if the simulation cell is bounded by two polarizable surfaces, the situation becomes much more difficult since the image construction results in an infinite set of image charges.…”

Section: Introductionmentioning

confidence: 99%

Simulations of Coulomb systems confined by polarizable surfaces using periodic Green functions

Santos

Girotto

Levin

2017

The Journal of Chemical Physics

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We present an efficient approach for simulating Coulomb systems confined by planar polarizable surfaces. The method is based on the solution of the Poisson equation using periodic Green functions. It is shown that the electrostatic energy arising from the surface polarization can be decoupled from the energy due to the direct Coulomb interaction between the ions. This allows us to combine an efficient Ewald summation method, or any other fast method for summing over the replicas, with the polarization contribution calculated using Green function techniques. We apply the method to calculate density profiles of ions confined between the charged dielectric and metal surfaces.

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“…Note that this concept exactly preserves the image charges needed to produce the electric field in the air. 26 Our calculations demonstrate that even with a small dielecric constant inside the particle, the charges at its water-exposed region can make a significant contribution to the long-ranged dipolar interactions between interfacially trapped particles. We analyze this behavior in terms of several parameters: the dielectric constant inside the particle, the potential difference across the air-water interface, and the salt content in the aqueous solution.…”

Section: Introductionmentioning

confidence: 74%

The apparent charge of nanoparticles trapped at a water interface

et al. 2016

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Charged spherical nanoparticles trapped at the interface between water and air or water and oil exhibit repulsive electrostatic forces that contain a long-ranged dipolar and a short-ranged exponentially decaying component. The former are induced by the unscreened electrostatic field through the non-polar low-permittivity medium, and the latter result from the overlap of the diffuse ion clouds that form in the aqueous phase close to the nanoparticles. The magnitude of the long-ranged dipolar interaction is largely determined by the residual charges that remain attached to the air- (or oil-) exposed region of the nanoparticle. In the present work we address the question to what extent the charges on the water-immersed part of the nanoparticle provide an additional contribution to the dipolar interaction. To this end, we model the electrostatic properties of a spherical particle - a nanoparticle or a colloid - that partitions equatorially to the air-water interface, thereby employing nonlinear Poisson-Boltzmann theory in the aqueous solution and accounting for the propagation of the electric field through the interior of the particle. We demonstrate that the apparent charge density on the air-exposed region of the particle, which determines the dipole potential, is influenced by the electrostatic properties in the aqueous solution. We also show that this electrostatic coupling through the particle can be reproduced qualitatively by a simple analytic planar capacitor model. Our results help to rationalize the experimentally observed weak but non-vanishing salt dependence of the forces that stabilize ordered two-dimensional arrays of interface-trapped nanoparticles or colloids.

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Interaction of Charged Colloidal Particles at the Air–Water Interface

Cited by 29 publications

References 49 publications

Thermodynamics and dynamics of two-dimensional systems with dipolelike repulsive interactions

Thermodynamics and dynamics of two-dimensional systems with dipolelike repulsive interactions

Simulations of Coulomb systems confined by polarizable surfaces using periodic Green functions

The apparent charge of nanoparticles trapped at a water interface

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